Centrifugal casting machine



June 24, 1930. .L B, ANDRSEN 1,767,035

CENTRIFUGAL CASTING MACHINE 24 z2 Filed May 28. 1928 INVENTOR w :sa 35 LAURlTz BANDRESEN '12ga Y 1&4 um

Awornoys Patented June 4, 1930 STATE-s PATENn ,OFFICE LAUBITZ B. ANDRESEN, OF MINNEAPOLIS,

MINNESOTA, kASSIGrNOIR T0 M. F. PATTER-- SON DENTAL SUPPLY C0., OF ST. PAUL, MINNESOTA, A CORPORATION .OF ILLINOIS Application led May 28,

This invention relates to new and useful improvements in centrifugal casting machines adapted for use in dental laboratories, in the art of preparing inlays, crowns, and other dental work.

Centrifugal ,casting machines, now commonly employed in dental laboratories, usually require that the gold or metal to be cast, be plated in an open Crucible supported in the machine, and heated with a blow torch until it is melted to the proper consistency, after which the casting machine `is manually started and the molten gold or metal is delivered, by centrifugal force, into a mold positioned adjacent to the crucible. This method of heating or melting the metal has proven unsatisfactory because no means' are provided for indicating to the person who is operating the machine, the tempera`V ture ofv the metal beore the machine is started and, consequently, the gold or metal is not always heated to the same temperature before it is delivered into the mold to be cast. v

It is now common practice for the person who is melting the gold, to observe it care-- fully asit is being heated, and' when it appears melted or heated to. the right temperature for casting, the machine is stmted,`

and the molten metal is delivered into the mold by centrifugal force. If the gold or .metal has not been sufliciently heated or melted Abefore the machine is started, the molten metal ma not enter the usual' small sprue hole. provi ed in the flask.'v Cnverselyif the metal is -overheated, it will burn the gold or metal, which will result'` inl the production of a 'poor casting andvin some cases, the metal cannot be cast at all. If it does ow into the flask, when thus burned, the resultant casting will usually be 'very rough. Also, if the gold has beenoverheated or burned, during they 'melting process, it will not produce a homogeneous castings.

1928. Serial No. 281,323.

rotation of the machine, when the vgold or metal has been heated to a predetermined temperature, thus eliminating all guesswork from the operation of preparing dental A further object is to pro'vide a centrifugal casng machine which will be entirely automatic in operation, from the standpoint of heating and melting the metal and start-- ing the machine, subsequent to placing the gold or metal within the heating chamber thereof.V t A A further object is to provide a centrifugal casting machine comprising a supportinoF bar mounted for rotary movement, in substantially a horizontal plane and normally retained in inoperative position, and

the member'having an electrically operated heating chamber mounted thereon adapted to receive the' metal to be cast, and means being associated with said heating chamber and responsive to temperature changes within the heating chamber, to automatically release' said bar from its retaining means, after a predetermined time interval, whereupon the bar will start to rotate, caqusinV the molten metal withinthe heating chamber to be delivered into a suitable mold or `flask, A,

base and having an armatureassociated with the bar-retaining member and havmg a cirsupply, a solenoid coil mounted upon the' .I l. ,90

cuit associated with the vheatin circuit and normally open, and a thermo-e ement beine'v mounted within the heating chamber and functioning to .close the solenoid circuit, after a predetermined time interval, whereupon the armature will be actuated to move the bar-retaining member out of locking engagement with the bar to ermit rotation of` A the bar andA heating cham er.

A further 'object is to provide a dental casting machine of the centrifugal type, comprising a base having a suitable motor mounted therein for mounted in the upper portion of the base -and adapted for rotary movement in substantially a horizontal plane, and a heating chamber being mounted upon the b ar adjacent to a mold suppoit ada )ted to demountaloly receive a mold or ask, which, when mounted upon the support, will. have its interioror cavity communicating with the heating chamber through a small sprue hole, and the bar normally being held in inoperative position by means of a retaining member operatively connected with a solenoid having a circuit electrically connected with the heating circuit for the heating chamber, and a thermo-element being associated with the heating chamber and responsive to temperature changes within the chamber, to effect the closing of the solenoid circuit, whereupon the solenoid will lnove the bar-retaining member out of engagement with the bar to permit the latter to rotate, and the actuation of said retaining member also automatically opening the solenoid and heating circuits, which circuits will thereafter remain open until the bar is again locked against rotation by moving the retaining member into engagement therewith.

A further object is to provide an electrically controlled dental casting machine comprising an electrically heated chamber adapted to receive the metal to be cast, and to melt the latter to the `desired degree for casting, the heating chamber being mounted upon a rotary bar which normally is locked against rotation by a locking member, and when said locking member is in bar-locking position, the heating circuit and also a solenoidv circuit will be conditioned for operation, andwhen current is supplied tothe heating circuit, the chamber will be heated to melt the` metal therein, and the rising temperature in the heating chambeil will ett'ect a thern'io-eleinent electrically connected with the heating and solenoid circuits, which will causethe closing of Athe solenoid circuit, after a predetermined time interval, whereupon the locking member will be actuated to release the bar and permit it to rotate, movement of the locking member also causing-the heating and solenoid circuitsto be opened. e

The particular object of the invention, therefore, is to provide a centrifugal casting machine having means for electrically heating the gold to a predetermined temperature, whereupon theinachine will be automatically started and the circuit to the heating coil opened, thus assuring that each casting will be of the saine consistency because the metal or gold nugget will be heated to the proper temperature to produce a perfect operating. a barl casting, before the machine is initiallystarted.

Other objects of the invention `vill appear fromv the following description and accompanying drawings and will be pointed out in the annexed claims.

l In the accompanying drawings, there has been disclosed a structure designed to' carry out the various objects of the invention, but

-it is to be understood that the invention is not confined to the exact features shown as various changes mav be made within the scope of the claims which follow.

In the accompanying drawings forming part of this specification; l

Figure, 1 is a diagrammatic sectional view illustrating the invention as applied to a there is illustrated a dental casting machine of the centrifugal type, comprising a housing 2 having a suitable flange 3 at the bottom thereof to provide means for securing it to a suitable support t, by such means as screws 5. A shaft 6 is rotatably mounted in a cap 7, suitably secured to the upper portion of the housing 2, and has its lower end operatively connected with a suitable spring motor 8, of ordinary construction. A bar 9 is secured to the upper end of the shaft 6 and is adapted for rotation in substantially a horizontal plane. A suitable ratchet device 10 is provided to permit the bar 9 to over-run, or continue rotating after the spring motor 8 has spent its energy.

The means provided for heating the metal or gold to be cast is shown at the left hand side of Figure 1, and comprises a heating chamber 11,. surrounded'by va heating coil 12 having conductorsl and 14 leading to suit able contact fingers 15 and 16, respectively,

mounted in an insulating block 1 7 secured to thebar 9. y I- y M A mold supprt 18 is adjustably mounted upon one end of the bar 9 adjacent to. the

heating chamber 11 by means of a suitableadjusting screw 19, received in a slot 2 lpi'o.- videdv in the bar.

cured vto thebar 9 so that the mold support and heating chamber maybe relatively adjusted with respect to one another, to accommodate the machine for various sizes of molds. In the drawings, there is shown a mold 23, of ordinary construction, positioned upon the mold support at`the outer end of the heating chamber. This mold is filled with the usual investment material 2t The heating chamber .11.` and coil 12 arc mounted within a suitablecasing 22 which preferably is adjustaloly-se-l is a o mounted in the insulat' and has a cavity`25 therein connected with" to engage contacts 29 and 31, electrically connected withY wires 32 and 33, respectively, which have contacts 34 and 35, respectively, connected therewith. These contacts are adapted to engage contact cli 36 and 37 electrically connected with t el main line conductors .38'and 39. .A switch 41 provides means for opening and closing the supply circuit to the apparatus. 1

-The means rovided for normally retaining the bar 9 in inoperative position, when the spring motor 8 is wound up, consists of a` rod 42 slidably mounted in suitable guides 43 and 44, provided respectivel in the cover 7 and housing 2, as shown in igure 1. This rod 42 functions to arrest movement of the bar 9, prior to starti the casting operation. An insulating4 bloc 45 is secured to the upper end of the rod 42 and provides a support for the contacts 29 and reviously described. A third contact 46 block 45 and has a wire 47 connecting it with one end of=a solenoid 48, here shown as being within. the housing 2. The other side of the .coil 48'has a wire 49connecting` it with the wire 33, shown in Figures 1 Aand 3.

An armature 51 is movably mounted within the solenoid coil 48 and has a recessed portion 52 adapted to receive one end of a lever 53, mounted upon a fixed pivot in 54. This lever has its opposite end pivota y connected to the lower end of the rod 42 by a pin 55, and has an end portion 56 projecting through a slot 57 in the housing, whereby it may be manually operated to move therod 42 into locking e agement with the bar- 9. Energizatioii of t e solenoid coil 48 will effect the automatic release of the bar 9, because of the upward movement of the armature 51 which will cause the shoulder 58 of the armature to enga the terminal of the lever 53, resulting in t e opposite end of the lever being moved downwardly with the resultant downward movement of the rod 42, and therefore the release of the bar 9. The armature is normally supported upon a suitable support 59.

An important feature of this invention resides in the means provided for automatically closing the solenoid circuit, after apredetermined time interval, subsequent to the placing of the metal or gold within the heating chamber 11.' Such means comprises a@ heating 'the heating coil l2.

thermo-element 60, preferably mounted within theheatingchamber 11 and having one end .fixed to the heating coil su porting means, as shown in Figure l, and aving a wire 61 connccti it with'a contact fin er 62 mounted -in the insulating block 17. he finger 62 is adapted to engage the contact 46. The opposite or movable end of the thermoelement 60 is mounted in a guide 63, of in sulating material, and is adapted to 'engage a contact screw 64 adjustably mounted in a small bracket 65, having a wire 66 connecting1 it with the wire 13 of the heating coil. o start the casting operation, the spring motor 8'is wound up by. manually rotating the bar 9, after which the locking member or rod 42 is moved upwardly from the position shown in Figure 2, to that shown in Figure-1, by means of the end` portion 56 of the lever k53. Such upward movement of the rod 42 will also move the contacts 46, 29, and 31 into electrical engagement with the contact fingers 62, 15, and 16, respectively, thereby conditioning the heating and solenoid circuits for starting.. When the chamber'is cold, the thermo-element will be *contracted as shown vin Figure 1, thereby leaving a gap 'between the movable terminal thereof and the contact screw 64. When the parts have been thus positioned, the metal or gold to be cast, indicated by the numeral 67 in' Figure l, is placed in the heating chamber 11, ate'r which the main switch 41 is moved into circuit-closin .posi-- tion, thereby causing current to flow t rough The heating circuit is asfollows; from the main line 'wiire 38 through the switch contacts 236-34, wire 32, contact 29, finger 15, conductor 13, heating coil 12, conductor 14, contacts 16-31, wire 33, contacts 35-37, and back'to the main line wire 39. Functioning of the heating coil will cause the temperature in the heating chamber to rise, thereby causing the thermo-element 60 to elongate and subsefiently electrically engage the terminal of t e contact screw 64. Such engagement of the thermo-element with the screw 64 will v eect the closing` of the solenoid coil 48, whereby the armature 51 will be drawn u wardly, causing the shoulder 58 to strike t eend of the lever 53 and move it upwardly into the dotted line position shown in Figure 1. Such movement of the lever 53 will cause therod 4 2 to be `.ioved downwardly to the position shown in Figure 2, causin the upper end thereof to be moved outl locking engagement with the bar 9, and, at the same time, movi the contacts 46, 29, 'and 31 out of electrical connection with the contact and solenoid coils to cease to function.

with the bar 9 will permit the motor vto fingers 62,15, and 16, respectively, as shown in igure 1, and thereby causing the heating- AMovement of the rod-42 out of engagement CYD rotate the bar, thereby causing the molten metal 67 to be delivered into the cavity 25 by the centrifugal action of the rapidly rotating bar 9.l The bar will continue to rotate until the motor has spent its energy.

It will therefore be seen that this novel casting machine is adapted for automatic operation, after the gold has initially been placed in the heating chamber 11, and the starting switch 4l is closed. Because of the contacts 46--29-31 being moved out of electrical connection with their respective contact fingers 62-15-16, the instant the bar 9 is released, no current will be consumed during the period of rotation of the bar, nor while the machine is at rest, thereby providing a very economical machine. The metal may be heated or melted to the required temperature lby adjustment of the Contact screw 64. p

In the drawings, I have shown this novel gold-melting and casting mechanism as aplied to an ordinary centrifugal machine, ut it is to be understood that it may be used in connection with various forms of dental casting machines without departing -rom the scope of the invention.

I claim as my invention:

1. A centrifugal casting machine provided with a heating chamber adapted to .receive themetal to be cast, a heating circuit for said chamber, a switch for closing said circuit to effect heating of said chamber, and means within said chamber responsive to temperature changes and adapted to eiect opening of said heating circuit, after a predetermined time interval.

2. A centrifugal casting machine provided with a rotary heating chamber adapted to receive the metal to be cast, a heating circuit for said chamber, a switch for closing said circuit to effect heating of the chamber, and means in said chamber responsive to temperature changes and adapted tov effect opening of said heating circuit and simultaneously to start rotation of the heating chamber.

3. A-centrifugal castin machine provided with a rotary heating ciamber adapted to receive the metal to be cast, a heating circuit for said chamber, locking means normally preventing rotation of said chamber, a solenoid circuit operatively associated with said locking means and said heating circuit, and a. thermo-element in said heating chamber responsive to temperature changes and adapted to ei'ect energization of the solenoid, whereby said locking means will be actuated to permit rotation of said heating chamber.

4. A centrifu al casting machine provided with a rotary heating chamber adapted to receive the metal to be cast, a heat-ing circuit for said chamber, locking means normally preventing rotation o said chamber,

r a solenoid having a circuit operatively associated with said locking means and said heating circuit, and a thermo-element in said heating chamber responsive to temperature changes and adapted to eii'ect energization of the solenoid upon a predetermined temperature in said chamber, whereby said locking means will be actuated to permit rotation of said heating chamber, actuation of said locking means also causing said heating and solenoid circuits to be opened.

5. A centrifugal casting machine provided with 'a rotary heating c amber adapted to receive the metal to be cast, a heating circuit for said chamber, locking means normally preventing rotation of said chamber, a solenoid having a circuit operatively associated with said locking means and said heating circuit, a thermo-element positioned adjacent a wall of said heating chamber and responsive to temperature changes in the chamber and adapted to close said solenoid circuit upon a predetermined temperature, whereby said locking means is actuated to permit rotation of said heating chamber,

actuation of said locking means also causing said heating and solenoid circuits to be opened.

6. A centrifugal casting machine comprising a rotatable bar, a driving means therefor, means for arrestin movement of said bar, a. mold demountaly secured to said bar, casing also secured to said bar and having heating chamber therein, a heating cir.

cuit for said chamber, a thermo-element associated with the chamber and responsive to temperature changes therein to eiect actuation o said locking means and whereby said bar is released and simultaneously said heating circuit is opened.

7. A centrifugal casting machine comprising a rotatable bar, a motor connected therewith and constantly tending to rotate the bar,

means for locking the bar against rotation,l

a mold and a casin adjustably secured to the bar, said casing having a heating chamber therein, a mechanism adapted to release said locking means, including a solenoid and circuit therefor, a thermo-element connected in series with said solenoid circuit and responsive to temperature changes in the heating chamber, and to cause actuation of said lock-releasing mechanism and to effect the release of said bar.

8. A centrifugal casting machine comprising a rotatable bar, a driving means therefor, means for arresting movement of said bar, a mold demountably secured to said bar, and havingan electric heating chamber in communication therewith, a normally open electric circuit associated with said arresting means, a contact in said circuit, and a thermo-element also in the circuit and responsive to temperature changes in said heating chamber whereby, when the temperature therein reaches a predetermined degree, said thermo-element will engage said Contact and close said circuit and cause said locking means to be o erated to release said bar.

9. A centrirugal casting machine comprising a rotatable bar, a motor connected there- I with, a locking member normally positioned in the path of said bar to prevent rotation thereof, a mold and a casing secured to the bar, said casing having an electric heatino' chamber therein communicating with said mold, an electrically operated device associated with said locking member and ada ted to release the latter, a circuit for said e'- vice, a contact at Yone end of the heating chamber electrically connected with said de# vice circuit, and a thermo-bar mounted in the chamber and connected with said device circut and adapted to engage 'sald contact, upon heating of said chamber, whereby said device circuit will be closed and said electric device operated to move said locking member out of engagement with said bar, to permit rotation thereof.

In witness whereof, I have hereunto set my hand this twenty second day of May, 1928.

LAURITZB. ANDRESEN. 

